The present invention relates to an electrophotographic photoreceptor (hereinafter occasionally referred simply to as a photoreceptor), and a processing cartridge as well as an image forming apparatus using said photoreceptor.
In recent years, as electrophotographic photoreceptors, organic photoreceptors comprising organic photoconductive materials have been most widely employed. The organic photoreceptors are superior to other photoreceptors in such a manner that it is easier to develop materials in response to various types of exposure light sources ranging from visible light to infrared light; it is possible to select materials which result in no environmental pollution; the production cost is lower; and the like. However, only one problem of the organic photoreceptors is mechanically weak and during copying a large volume as well as during printing, the photoreceptor surface results in degradation as well as abrasion.
Such photoreceptors are generally prepared employing the following method. A charge generating layer is prepared by vacuum-evaporating organic charge generating materials onto an electrically conductive support which is comprised of aluminum or an aluminum alloy, or by applying a coating composition prepared by mixing organic charge generating materials with organic polymeric resins as the binding agent onto said support. Subsequently, a charge transport layer is formed by applying a coating composition, prepared by mixing organic charge transport materials and organic polymeric resins as the binding agent with a solvent onto the resulting charge generating layer.
In recent years, demand for electrophotographic image forming apparatuses has become more stringent in regard to image quality. Specifically, for reversal development type printers such as LD and LED printers and the like, still higher printing quality is desired. For instance, it is desired to eliminate minute black points (so-called black spots), which are formed on white backgrounds, and the like.
Generally, in electrophotographic copiers utilizing the Carlson method, after uniformly charging a photoreceptor, the resulting charge is eliminated imagewise by exposure to form an electrostatic latent image, which is developed employing toner and visualized. Subsequently, the toner is transferred onto paper and the like, and then fixed.
However, all toner on the photoreceptor is not transferred and a small portion of the toner remains on the photoreceptor. When images are repeatedly formed in such a state, the residual toner adversely affects the formation of the latent images. As a result, it is impossible to obtain high quality image copies without staining. Therefore, it is required to remove the residual toner. Representative cleaning means include a fur brush, a magnetic brush, a blade, and the like. Of these, a blade is mainly employed from the viewpoint of the performance, constitution, and the like. As the blade member, a plate-shaped rubber elastic body is generally employed.
As described above, electrical and external mechanical forces are directly applied to the surface of the electrophotographic photoreceptor through the charging unit, the development unit, the transfer means, the cleaning unit, and the like. Accordingly, durability against these processes is essential. Specifically, mechanical durability is required to counter the wear and abrasion of the photoreceptor surface due to sliding, as well as film peeling and the like, due to impact and the like, during corrective action to remove foreign matter and undo paper jams. Of these, durability similar to inorganic photoreceptors is strongly demanded against flaws due to impact, as well as film peeling.
In order to realize the various desired properties as described above, heretofore, various items have been investigated.
In order to improve the aforementioned image quality, proposed is a photoreceptor in which an alumite layer as a boundary blocking layer, which retards charge injection to the photosensitive layer, is formed on the surface of the aluminum base plate as the electrically conductive support. When such an alumite layer is employed, image quality, due to reduction of black spots and the like, is improved. However, since its close adhesion with the photosensitive layer decreases, durability of the photosensitive layer surface against external mechanical force also decreases. As a result, problems such as flaws, as well as film peeling, occur. It has been difficult to dissolve such problems of the film peeling caused by decrease of close adhesion with the photosensitive layer.
As far as the durability against mechanical force concerns, it is reported that wear resistant properties of the surface, as well as toner filming properties, are improved by employing BPZ polycarbonate as the binder (a binding resin) on the surface of the organic photoreceptor. Further, Japanese Patent Publication Open to Public Inspection No. 6-118681 discloses colloidal silica containing hardenable silicone resin employed as the protective surface layer of a photoreceptor.
However, a photoreceptor comprising the bisphenol Z type polycarbonate binder exhibits insufficient wear resistant properties and also does not exhibit sufficient durability. On the other hand, improved are wear resistant properties of the surface layer comprised of the colloidal silica containing hardenable silicone resin. However, electrophotographic properties are unsatisfactory during repeated use, and background staining as well as blurred images tends to occur. Thus, this method does not exhibit sufficient durability. Namely durability is not insufficient in each case, particularly it is difficult to prevent peeling due to deterioration of sdhesion of alumite layer and the photosensitive layer.
Japanese Patent Publication Open to Public Inspection Nos. 9-124943 and 9-190004 disclose a photoreceptor having as the surface layer, a resin layer in which an organic silicone modified positive hole transport compound is bonded to a hardenable organic silicone based polymer. However, said resin layer tends to form background staining as well as blurred images at a relatively high humid ambiance. Thus sufficient durability is not obtained. Further, said hardenable organic silicone compound film exhibits high wear resistant properties. However, since said film tends to suffer from flaws due to external impact and tends to peel, its strength, as well as adhesion, is not sufficient.
Further, accompanying the recent progress of digital technology, in the image forming methods employing electrophotography, image exposure utilizing an interfering light source has been the main process. Thus, desired has been the development of a photoreceptors which are suitable for such an interfering light source and do not form an interference moire; exhibit high wear resistance, and neither suffer from flaws nor peel due to external impact; and further does not form blurred images.
It is an object of the present invention to dissolve problems caused by decrease of close adhesion of the photosensitive layer with alumite layer. For this purpose, it is the object to provide a photoreceptor having high surface hardness. It is an object of the present invention to provide, while overcoming the problems described above, an electrophotographic photoreceptor which exhibits high surface hardness, high wear resistance, and high flaw resistance; exhibits consistent electrophotographic properties at high temperature and humidity during repeated use, and accordingly, repeatedly produces excellent images, and does not form a moire during the formation of digital images employing a laser beam and the like, and further to provide a processing cartridge as well as an image forming apparatus employing said photoreceptor.
The inventors of the present invention have endeavored to overcome the problems described above, in particular to maintain close adhesion of the photosensitive layer even when alumite is employed. As a result, it was discovered that the purpose of the present invention was achieved, that is, to dissolve close adhesion of the photosensitive layer with alumite layer, namely film peeling, by enhancing surface hardness of the photoreceptor in which a specified resin layer. Doubt to tear the surface layer of the photoreceptor by, for example, cleaning blade decreases, and stress does not applied to the alumite layer and photosensitive layer because the specified resin layer has high hardness. Conventional problems have been improved by this.
Further, degree of light scattering is controlled by maintaining surface roughness of substrate of the photoreceptor beneath photosensitive layer within predetermined surface roughness for the purpose of preventing occurrence of moire in forming digital image employing laser light etc. However the above mentioned surface roughness of the substrate of the photoreceptor itself induces asperity at the surface of the substrate. In such condition cleaning blade should be pressed by strong pressure to the photoreceptor to perform sufficient cleaning. It has been found that wear and film peeling of photoreceptor surface are dissolved by forming a specified resin layer on the surface of the photoreceptor. In the present invention it becomes possible that problems such as durability and film peeling as well as preventing occurrence of moire by a combination of controlling surface roughness of substrate and the above mentioned specified resin layer.
The invention and its embodiments are described below.
In an electrophotographic photoreceptor comprising an electrically conductive support having thereon a photosensitive layer, an electrophotographic photoreceptor wherein the surface layer of said electrophotographic photoreceptor comprises a hardenable siloxane resin having charge transportability, and said electrically conductive support comprises on its surface a sealed alumite film.
In an electrophotographic photoreceptor comprising an electrically conductive support having thereon a photosensitive layer, an electrophotographic photoreceptor wherein the surface layer of said electrophotographic photoreceptor comprises a hardenable siloxane resin comprising a partial structure having charge transportability and said electrically conductive support comprises on its surface a sealed alumite film.
Said partial structure having charge transportability is preferably represented by the structural formula described below. 
wherein X represents a charge transportability providing group which bonds to Y via a carbon atom constituting of said providing group, and Y represents a divalent or higher valent atom or group excluding adjacent bonding atoms (Si and C).
Said partial structure having charge transportability is preferably represented by the structural formula shown below. 
wherein X is a charge transportability provided group, which bonds to Y via a carbon atom constituting said providing group, and Y represents an oxygen, a sulfur atom, or NR, wherein R represents a hydrogen atom or a univalent organic group.
In an electrophotographic photoreceptor comprising an electrically conductive support having thereon a photosensitive layer, an electrophotographic photoreceptor wherein the surface layer of said electrophotographic photoreceptor is comprised of a resin layer containing a hardenable siloxane resin obtained by allowing an organic silicon compound having a hydroxyl group, or a hydrolyzable group, to react with a charge transferable compound having a hydroxyl group, and said electrically conductive support comprises on its surface a sealed alumite film.
In an electrophotographic photoreceptor, comprising an electrically conductive support having thereon a photosensitive layer, an electrophotographic photoreceptor wherein the surface layer of said electrophotographic photoreceptor is comprised of a resin layer containing a hardenable siloxane resin obtained by allowing an organic silicon compound having a hydroxyl group or a hydrolyzable group to react with a charge transferable compound having an amino group, and said electrically conductive support comprises on its surface a sealed alumite film.
In an electrophotographic photoreceptor comprising an electrically conductive support having thereon a photosensitive layer, an electrophotographic photoreceptor wherein the surface layer of said electrophotographic photoreceptor is comprised of a resin layer containing a hardenable siloxane resin obtained by allowing an organic silicon compound having a hydroxyl group or a hydrolyzable group to react with a charge transferable compound having a mercapto group, and said electrically conductive support comprises on its surface a sealed alumite film.
An electrophotographic photoreceptor wherein said resin layer containing a hardenable siloxane resin is hardened.
An electrophotographic photoreceptor wherein said photosensitive layer is comprised of a charge generating layer as well as a charge transport layer.
An electrophotographic photoreceptor wherein said photosensitive layer is comprised of a charge generating layer as well as a charge transport layer.
An electrophotographic photoreceptor wherein an interlayer is provided between said electrically conductive support and said photosensitive layer.
An electrophotographic photoreceptor wherein the thickness of said surface layer is between 0.1 and 20 xcexcm.
An electrophotographic photoreceptor wherein an adhesive layer is provided between said surface layer and the adjacent layer.
An electrophotographic photoreceptor wherein said charge transportability providing group is a triarylamine based compound residual group.
An electrophotographic photoreceptor wherein said charge transportability providing group is a hydrazone based compound residual group.
An electrophotographic photoreceptor wherein said charge transportability providing group is a styryltriphenylamine based compound residual group.
An electrophotographic photoreceptor wherein said charge transportability providing group is a benzidine based compound residual group.
An electrophotographic photoreceptor wherein said charge transportability providing group is a butadiene based compound residual group.
An electrophotographic photoreceptor wherein said interlayer is a resin layer.
An electrophotographic photoreceptor wherein said interlayer is a resin layer formed by allowing an organic metal compound to react with an organic metal chelate compound.
An electrophotographic photoreceptor wherein said electrophotographic photoreceptor comprises an antioxidant.
An electrophotographic photoreceptor wherein said antioxidant is a compound having a partial structure of hindered phenol, hindered amine, thioether, or phosphite.
An image forming apparatus wherein an electrophotographic photoreceptor is employed, and an image is formed through charging, image exposure, development, transfer, separation, and cleaning.
Ten points average surface roughness (Rz) of the conductive support is preferably not less than 0.3 xcexcm and not more than 2.5 xcexcm.
In a processing cartridge employed in an image forming apparatus which carries out the processes of charging, image exposure, development, transfer, separation, and cleaning while employing an electrophotographic photoreceptor, a processing cartridge which is produced by combining said electrophotographic photoreceptor with at least one of any of a charging unit, an image exposure unit, a development unit, or a cleaning unit.